Note: for HOTs the final effect is spread evenly across all ticks. Druid HOTs last 12s and Priest's last 15s so druids get 80% effect and priests get 100% healing effect on their hots.

Also, for those who think that +healing has less of an effect on a 1.5 second cast spell than a 3.5 second cast spell you are incorrect. That is, not factoring in any talents that lower cast times of your spells. Lets compare a 1.5s heal and a 3s heal with +100 healing effect

(1.5/3.5) = 0.428 * 100 = 42.8 healing bonus per 1.5s

(3/3.5) = 0.857 * 100 = 85.7 healing bonus per 3s

If you cast the 1.5s heal 2 times you get an effective 85.7 bonus healing, same as the 3s heal.